In the electronics field, ferroelectrics are applied to a variety of devices including IR detecting devices, piezoelectric devices, optical modulators, optical memories, etc. In recent years, ferroelectric devices in film form have been increasing with increasing demands for miniaturized electronic components due to the progress of semiconductor technology.
In the case of ferroelectric devices such as pyroelectric IR detecting devices and piezoelectric devices, from which changes in the spontaneous polarizations, Ps, of ferroelectrics are taken out as output, a largest value of the output can be obtained when the Ps's of each ferroelectric material are unidirectional. However, ferroelectric porcelains used today in IR detecting devices, piezoelectric devices, and the like are polycrystalline materials, in which the crystals are oriented in various directions, and hence the individual spontaneous polarizations, Ps, of each crystal are oriented at random. In each of epitaxial ferroelectric films and oriented ferroelectric films, the polarization axes of the crystals are uniform in direction but electrical spontaneous polarizations, Ps, form 180.degree. domains that are oriented alternately in opposite directions. Therefore, when these materials are used in such electronic devices as mentioned above, the poling treatment of applying a high electric field (.about.100 KV/cm) to make each material is necessary in order to uniform the directions of spontaneous polarizations, Ps.
This poling treatment method raises the following problems:
(1) The poling treatment may cause the dielectric breakdown of materials treated, hence lowering the yield.
(2) It is difficult to pole uniformly a great number of fine ferroelectric elements arranged in a high density as in high-resolution array devices.
(3) The poling treatment itself is impossible in certain cases of integrated devices comprising ferroelectric films formed on semiconductor devices.
There are a number of reports on the formation of films of PbTiO.sub.3, PLZT, and the like. With respect to these films, however, none of these reports reveal the process for producing a film in which c-axes that are polarization axes are oriented unidirectionally. Moreover, the process for producing a material in which also spontaneous polarizations are oriented unidirectionally is not clarified at all.